Study: Testosterone Supplements Can Be SafeAn increasing number of aging men think they've found the way to feel young again -- by taking supplements of the male hormone testosterone. But doctors worry that testosterone supplements could increase the risks of prostate cancer. A new study offers some reassurance without completely absolving the hormone.

An increasing number of aging men think they've found the way to feel young again — by taking supplements of the male hormone testosterone. But doctors worry that testosterone supplements could increase the risks of prostate cancer.

A study in this week's Journal of the American Medical Association offers some reassurance, but it doesn't completely absolve the hormone.

Men reach their testosterone peak at about age 30. After that, levels in the blood decrease by about one percent a year. That means that a 65-year-old man could easily have about one-third less testosterone than he did when he was younger.

There have been no conclusive studies proving that testosterone has helped men in that position.

Most studies are small and short-term. Some have even suggested risk: an increase in red blood cell production, which can thicken blood and make patients more vulnerable to heart attack and stroke. There are also concerns about prostate cancer.

But researchers at UCLA find that after six months of use, the hormone does not appear to affect prostate tissue.

Urologist Dr. Leonard Marks, who headed the study, says, "The placebo-treated men actually had more cancers than the testosterone-treated men — all small cancers, but some were clinically significant. But there was certainly no carcinogenic effect of [testosterone therapy] that we could identify."

Marks says the study is good news for short-term use of testosterone — to help build muscle mass in burn patients, for example — or for HIV patients suffering from wasting syndrome. But Marks says the study was small, just 44 men. So, the safety of long term use, he says, is still a question.